Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
  • D21H17/675—Oxides, hydroxides or carbonates
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
  • D21H11/08—Mechanical or thermomechanical pulp
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
  • D21H17/68—Water-insoluble compounds, e.g. fillers, pigments siliceous, e.g. clays
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/70—Inorganic compounds forming new compounds in situ, e.g. within the pulp or paper, by chemical reaction with other substances added separately
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
  • D21H25/08—Rearranging applied substances, e.g. metering, smoothing; Removing excess material
  • D21H25/12—Rearranging applied substances, e.g. metering, smoothing; Removing excess material with an essentially cylindrical body, e.g. roll or rod
  • D21H25/14—Rearranging applied substances, e.g. metering, smoothing; Removing excess material with an essentially cylindrical body, e.g. roll or rod the body being a casting drum, a heated roll or a calender

Definitions

• the printing paper product is paper intended to be printed by printing machines and manufactured, for example, for magazines and newspapers.
• the printing paper product may be coated, such as LWC paper, or uncoated, such as SC paper or newsprint.
• the main raw material for a printing paper product is usually natural fibre, for example mechanically pulped natural fibre, chemically pulped natural fibre, and/or recycled fibre.
• SC super calendered
• LWC light weight coated
• the printing paper product according to the invention comprises continuously precipitated calcium carbonate (CPCC), whose addition is integrated in the papermaking process.
• CPCC continuously precipitated calcium carbonate
• the method according to the invention for manufacturing a printing paper product is primarily characterized in what will be presented in claim 5.
• the system according to the invention for manufacturing a printing paper product is primarily characterized in what will be presented in claim 14.
• the printing paper product according to the invention is primarily characterized in what will be presented in claims 1 and 20.
• An advantageous embodiment of this invention relates particularly to wood containing, that is mechanically pulped natural fibre containing uncoated printing paper products..
• Such established properties set for the final product which must have certain values according to the requirements, include, for example, paper density before calendering, paper density after calendering, fluffi- ness and rigidity of the paper, strength properties of the paper, such as for example tensile strength, tear strength, surface resistance, and z-strength, as well as properties relating to printing, such as printed gloss, gloss contrast, print evenness, and absorption property of the paper.
• Factors affecting the cost include for example the raw materials as well as their processing, and the technical solutions of the production technology and the operation parameters of the production process.
• the present invention relates most advantageously to supercalendered paper, that is, SC paper.
• SC paper is uncoated calendered magazine paper.
• the filler content in the final product is nowadays already relatively high, typically about 25 to 33 wt-%, depending on the grammage of the final product.
• filler is included in a mechanically and/or chemically pulped fibre suspension by adding milk of lime and carbon dioxide, for precipitating calcium carbonate on the surfaces of natural fibres.
• calcium carbonate is precipitated on the surfaces of fibre particles by first admixing carbon dioxide to the fibre fraction and then adding lime of milk.
• carbon dioxide is precipitated on the surfaces of fibre particles by first admixing lime of milk to the fibre fraction and then precipitating the lime of milk with carbon dioxide to form calcium carbonate on the surfaces of the fibre particles.
• mechanically pulped natural fibre or so-called mechanical pulp is divided into at least two fibre fractions before precipitating calcium carbonate in connection with at least one of said fibre fractions.
• chemically pulped natural fibre is divided into at least fibre fractions before calcium carbonate is precipitated in connection with at least one of said chemically pulped fibre fractions.
• a gradient calender is used for calendering a printing paper product, to achieve a printing paper product with low density.
• the gradient calender is a temperature gradient calender and/or a moisture gradient calender.
• the grammage of the printing paper product according to the invention is suitably in the range of 27 to 70 g/m 2 , preferably in the range of 35 to 60 g/m 2 .
• the printing paper product according to the invention is calendered and uncoated with a pigment, having a grammage of 27 to 70 g/m 2 , preferably 35 to 60 g/m 2 .
• a pigment having a grammage of 27 to 70 g/m 2 , preferably 35 to 60 g/m 2 .
• it contains at least mechanically pulped natural fibres and precipitated calcium carbonate as a filler.
• the filler content in said printing paper product is
• the method according to the invention for manufacturing a printing paper product natural fibres are introduced in a system comprising a paper machine. Furthermore, the method advantageously comprises
• a printing paper product by said paper machine comprising at least said natural fibres as well as precipitated calcium carbonate as a filler in said printing paper product.
• the term natural fibre is used, referring to various fibres of natural origin.
• the natural fibre may be, for example, mechanically pulped fibre, dissolving cellulose fibre, sulphite cellulose fibre, sulphate cellulose fibre, or viscose fibre.
• the natural fibre is selected from the group of wood-based fibres, fibres of plant origin, and their derivatives and mixtures.
• the natural fibre is selected from the fibres of wood, sisal, jute, hemp, flax, straw, and other annual plants, as well as mixtures of these.
• the printing paper product according to the invention comprises wood fibres as the main raw material.
• the content of natural fibres in the finished (dry) printing paper product is advantageously not higher than 80 wt-%, more advantageously not higher than 70 wt-%, but preferably at least 50 wt-%.
• said natural fibre has been subjected to chemical treatment to reduce the lignin content.
• the invention utilizes bleached TMP which has been fractionated into at least two separate fibre fractions before precipitating calcium carbonate onto the surface of at least one fibre fraction.
• the printing paper product according to the invention may comprise chemi- cally pulped natural fibres, which are also called chemical pulp in this application.
• the raw material for a chemically pulped fibre fraction has been pine, spruce, birch, eucalyptus, and/or acacia.
• the filler in the printing paper product comprises precipitated calcium carbonate.
• Ca(OH) 2 in continuous precipitation of calcium carbonate, calcium carbonate is precipitated in connection with a selected material in such a way that calcium carbonate adheres at least partly to the surfaces of said material.
• the solution according to the invention always comprises a step in which calcium carbonate is precipitated from calcium hydroxide Ca(OH) 2 in a continuous process (continuous precipitated calcium carbonate, CPCC), in such a way that calcium carbonate is precipitated onto the surfaces of mechanically pulped natural fibres.
• the reactive mineral material used for said filler is calcium hydroxide, advantageously an aqueous solution of calcium hydroxide, which is also called milk of lime (MOL).
• the precipitating chemical used for said filler is advantageously carbon dioxide, preferably pure or almost pure carbon dioxide (degree of purity preferably 85 to 100%).
• mechanical pulp and/or chemical pulp is divided into at least two different fractions.
• one or more physical properties in said at least two different pulp fractions differ substantially from each other.
• Said different physical property in the fractions may comprise one or more of the following: fibre length distribution,
• both the reject from the classifier 3 and the accept from the classifier 3 of at least classifying step are prefera- bly utilized in the actual paper manufacture. If the system comprises several classifying steps, at least the last classification preceding the precipitation of calcium carbonate is preferably performed for such pulp that can be utilized in whole or substantially in whole for manufacturing a printing paper product 1.
• the mechanical pulp 2a used as the raw material may be pulp bleached already before it is supplied into the process according to the invention, and/or it can be bleached in the process according to the invention.
• the bleaching of the mechanical pulp 2a is done in a process in which lignin causing blackening of the fibre raw material is diluted with chemicals.
• Such a bleaching process may be, for example, peroxide bleaching.
• mechanical pulp is divided into at least two fractions or fibre fractions before a separate bleach- ing step (not shown in the figures), after which one or more fibre fractions are led into said bleaching process.
• said bleaching process is carried out on homogeneous mechanical pulp.
• the classification into at least two fibre fractions is suitably performed after the last bleaching step.
• the bleaching of mechanically pulped natural fibres is suita- bly performed before the step of precipitating calcium carbonate.
• Mechanically pulped natural fibre 2a i.e. mechanical pulp
• chemically pulped natural fibre 2b i.e. chemical pulp
• Figures 1 show the division of natural fibre raw materials 2a, 2b into only two fractions or fibre fractions, although there may also be more fibre fractions. Furthermore, it is possible that no chemical pulp 2b is used at all.
• the partial fractions can also be returned to the system in a different order than that shown in the figures. The partial fractions can be returned to substantially the same process step, or they can be returned to different steps in the process.
• the printing paper product comprises, in addition to precipitated calcium carbonate, at least one inorganic pigment 2c other than said precipitated calcium carbonate.
• calcium carbonate may have been precipitated to said inorganic pigment 2c by precipitation means 4.
• lime of milk and carbon dioxide are supplied to an aqueous solution of the inorganic pigment 2c, for precipitating calcium carbonate onto the surfaces of said inorganic pigment.
• a new hybrid pigment is formed, in which said inorganic pigment is coated at least partly with precipitated calcium carbonate.
• said inorganic pigment is selected from titanium dioxide, kaolin, talc, milled calcium carbonate, chalk, feldspar, mica, and waste pigment flow from a deinking plant.
• the fractioning of the mechanical pulp 2a and/or the chemical pulp 2b with the classifier 3 into at least two fractions before the precipitation of calcium carbonate can be performed with a classifier of prior art.
• said chemical treatment 5 as well as said precipitation 4 of calcium carbonate are performed for at least one and the same fibre fraction.
• the adherence of the filler formed onto the surfaces of the natural fibre raw material in the calcium carbonate precip- itation reaction 4 (CPCC) is intensified by a chemical treatment by dosing one or more chemicals into one or more fibre fractions in which calcium carbonate is precipitated (not shown in the figures).
• said chemical to enhance the adherence is selected from starch, cationic starch, xylan, galactoglucomannan, calcium hydroxide, peracetic acid, or other reacting chemicals, as well as other polymers with a long-chained and/or branched molecular structure, as well as various modifications of the above mentioned chemicals.
• said chemical treatment 5 and the precipita- tion 4 of calcium carbonate are performed for different fractions.
• the chemically treated fraction is returned to a different step in the process compared with the fraction in which calcium carbonate has been precipitated.
• the retention time of said chemically treated fraction in the process may be substantially different from the retention time of at least one other fraction.
• the chemical treatment 5 is implemented for a short fibre fraction.
• at least one chemically treated fibre fraction is led, after said chemical treatment 5, to the short cir- culation of the paper machine.
• the chemically treated fraction is introduced into the so-called headbox feed pump of the paper machine.
• the chemically treated fraction is led to the so-called mixing tank.
• This reduc- tion may be, for example, at least 10 percentage units or at least 20 percentage units compared with a situation without the method according to the invention for producing a filler.
• the contents of interfering substances can be detected, for example, by measuring them on component level, for example, as contents in ppm.
• the required quantity of retention material after the precipitation reaction is about 30% lower compared with a situation without the method of manufacture according to the invention.
• the printing paper product 1 according to the invention is formed by mixing all the different partial fractions to a pulp suspension upstream of the paper machine 7 and by leading this pulp suspension to the paper machine, for forming a paper product.
• the printing paper product 1 according to the invention is formed by leading the above described partial fractions, either as such or partly mixed with each other, to the paper machine 7, to form a printing paper product with a layered structure.
• the desired partial fractions can be led to the middle layer of the printing paper product, and the desired partial fractions to the surface layers of said paper, for example by means of a multilayer headbox. In this way it is possible to optimize the structure of the paper.
• the fractions which improve the bulk and/or the strength in the z-direction are led to the middle layer of the paper, and the fractions which improve printability are led to the surface layers.
• the infiltration of the web formed of the pulp suspension supplied in the form of partial fractions or a single frac- tion to the paper machine is performed at least partly by means of a planar band and/or surfaces provided with holes or perforations, and dewatering elements in the forming section.
• the method according to the invention comprises one or more of the following steps in a predetermined order.
• the final product formed is an uncoated printing paper product, such as, for example, magazine paper or newsprint, most advantageously supercalendered (SC) paper, which contains precipitated calcium carbonate as a filler and mechanically pulped natu- ral fibres as the main fibre raw material.
• the printing paper product may contain chemically pulped natural fibres. At least part of said mechanically pulped natural fibres and/or chemically pulped natural fibres are at least partly coated with precipitated calcium carbonate.
• the printing paper product may contain at least one other filler. In an example, calcium carbonate is precipitated in at least one other filler.
• the SC paper according to the invention is gradient calendered in such a way that the density of the product after the calendering is lower than 1100 kg/m 3 , more preferably less than 1050 kg/m 3 , and most preferably lower than 1000 kg/m 3 . Thanks to the gentler calendering than conventionally, the stiffness and optical properties of the SC paper may be improved. Furthermore, the tear strength of the paper may remain on a higher level, thanks to the lower linear load caused by the gentler calendering.
• the higher tear strength level may contribute to enable a reduction in the pulp content in the raw materials of the paper without causing problems in, for example, the runnability of the final product in the printing works, and/or an increase in the filler content.
• the calendering of the printing paper product is performed with a so-called gradient calender.
• very small drops of water, or spray water is applied onto the paper web.
• the paper web can be subjected by the calender rolls and/or steam boxes to a high temperature, for directing the surface forming effect of calendering primarily to the surface of the paper to be calendered.
• the density of the paper after the calendering can be brought to a lower level than normally.
• the content of mechanical pulp in the natural fibres used in the printing paper product is thus at least 70 wt-%, at least 80 wt-% or at least 90 wt-%, and more advantageously 100 wt-%.
• the mechanical pulp consists at least primarily of TMP.
• the SC paper according to the invention contains about 2 to 4 percentage units more fillers than SC paper of prior art.
• the filler content of SC paper according to the invention follows the formula
• Y > 0.897x - 12.5, preferably the formula: Y > 0.897x - 10, in which formulae Y represents the filler content and x represents the gram- mage.
• Y represents the filler content
• x represents the gram- mage.
• the density of calendered SC paper according to the invention follows the formula:
• the printing paper product according to the invention has at least some or all of the properties listed below:
• the printing paper product is SC paper.
• the printing paper product is uncoated.
• the printing paper product is calendered.
• the grammage of the printing paper product is suitably 27 to 70 g/m 2 , preferably in the range from 35 to 60 g/m 2 .
• 52 g/m 2 is suitably lower than 1100 kg/m 3 ,
• the density of a printing paper product of, for example, 52 g/m 2 is suitably lower than 1050 kg/m 3 .
• the gloss of the calendered printing paper product is, for example for a paper of 52 g/m 2 , at the level of 49 ⁇ 4, and for example for a paper of 41 g/m 2 , at the level of 41 ⁇ 4, defined by Hunter Gloss 75° measurement.
• the porosity (Bendtsen) of the calendered printing paper product is, for example for a paper of 52 g/m 2 , at the level of 19 to 27 ml/min, and for example for a paper of 41 g/m 2 , at the level of 32 to 40 ml/min.
• the smoothness (PPS10) of the calendered printing paper product is, for example for a paper of 52 g/m 2 , at the level of 1.0 to 1.2 ⁇ , and for example for a paper of 41 g/m 2 , at the level of 1.18 to 1.36 ⁇ ⁇ ⁇ .
• the strength of the calendered printing paper is at a level sufficient for runnability at a printing works.
• Example 1 presents some properties of SC paper manufactured by the method according to the invention.
• Figures 2 to 5 show an example of the filler content in relation to the gram- mage of the printing paper product according to the invention.
• Figure 2 shows a comparison between two SC papers, of which one (number 1 ) has been made by the method of the invention and the other (number 10) by a method of prior art. Both products have corresponding strength properties (tear strength, tensile strength, z-strength).
• the density of the paper made by the method of the invention is lower than 1100 kg/m 3
• the density of the paper of prior art is higher than 1100 kg/m 3 .
• the filler content of the printing paper product according to the invention is about 4 percentage units higher than for the paper of prior art.
• Figure 3 shows an advantageous minimum filler content and the most advantageous minimum filler content for the product according to the invention, in relation to the grammage.
• Figure 4 shows an advantageous maximum density and the most advanta- geous maximum density of the calendered printing paper product according to the invention, in relation to the grammage.
• Figure 5 shows the relation of brightness to opacity for SC paper according to the invention, with a grammage of 52 g/m 3 .
• the uppermost line in the figure represents a situation in which the filler content of the product according to the invention is 4% higher than in products of prior art and the product is cal- endered by gradient calendering.
• the middle line represents a situation in which the filler content of the product according to the invention has been raised by 2% with respect to products of prior art, and the product has been calendered by a conventional 12-roll supercalender.
• the lowermost line rep- resents the properties of SS paper of prior art.
• the method according to the invention can be used to manufacture SC paper in a cost efficient way so that the product has a considerably high filler content and a low density, that is, a high bulk.
• the SC paper according to the invention can still obtain the printing and strength properties that meet the requirements.
• the optical properties of SC paper according to the invention can be considerably improved.
• opacity and brightness can improve by 1 to 3 percentage units compared with corresponding values for known products having a high density (>1 100 kg/m 3 ) and a conventional filler content (20 to 33 % in the grammage range of 35 to 60 g/m 2 ).
• the method according to the invention has several advantages.
• the novel method according to the invention allows a higher filler content and/or a lower content of chemically pulped natural fibre (pulp) compared with paper grades manufactured by techniques of prior art.
• the method according to the invention also makes it possible to reduce the specific energy consumption com- pared with a similar product manufactured by techniques of prior art.
• an uncoated calendered printing paper product whose concurrent properties may include a higher filler content than at present, a lower density level than at present, and still substantially equally good printing surface properties (smoothness, opacity, brightness).

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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Paper (AREA)

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• 2011
  • 2011-06-21 FI FI20115637A patent/FI124859B/fi active IP Right Grant
• 2012
  • 2012-05-29 EP EP20120803369 patent/EP2723944A4/en not_active Withdrawn
  • 2012-05-29 JP JP2014516403A patent/JP2014520215A/ja not_active Ceased
  • 2012-05-29 WO PCT/FI2012/050523 patent/WO2012175788A1/en active Application Filing
  • 2012-05-29 US US14/128,759 patent/US9085854B2/en not_active Expired - Fee Related

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